Recent nutritional studies have indicated prevalent marginal deficiency of vitamin B6 in many segments of the American population. While the consequences of long-term marginal status are unclear, vitamin B6 nutriture is known to affect the efficiency of many physiological processes and host defense mechanisms. Because of a lack of knowledge of the bioavailability of vitamin B6, the adequacy of human diet in meeting the nutritional requirement often cannot be determined. Recent studies indicate that the proportion of pyridoxine beta-glucoside (PN-G) may be a major determinant of the bioavailability of dietary vitamin B6. This research will involve a characterization of the nutritional properties of PN-G, which comprises a major portion of the vitamin B6 of plant-derived foods. The following objectives will be addressed: (1) The relative utilization of suboptimal levels of PN-G will be determined relative to pyridoxine (PN) in a rat bioassay using specific metabolic indicators of vitamin B6 status. (2) The influence of vitamin B6 nutriture and intestinal microflora on PN-G utilization will be determined by examination of the metabolism of orally or intravenously administered differentially radiolabelled PN-G and PN in vitamin B6 deficient or adequately nourished rats. (3) The extent of secretion of PN-G or its metabolites in the milk of lactating rats will be examined to determine the potential role of PN-G in the nutrition of the offspring. Radiolabelled PN and PN-G in the maternal diet will be compared as sources of available vitamin B6 for rat pups. (4) Human subjects will be employed in a study of the relative utilization of deuterium-labelled PN (d5) and PN (d2). The urinary excretion of deuterated forms of 4-pyridoxic acid and intact PN-G will be reflective of PN and PN-G utilization in vitamin B6 metabolism. The results of these studies will permit a more accurate evaluation of vitamin B6 nutrition by providing detailed information concerning the absorption and metabolism of PN-G.